Drought Wheat - getting more crop per drop

For many farmers, developing drought-resistant strains of wheat means the difference between surviving the next "Big Dry", or, leaving the land. Now there's new hope, thanks to the chance meeting of two plant scientists who approach the problem from very different directions.

Broadcast:
Thu 3 May 2007, 8:00pm

Published:
Thu 3 May 2007, 8:00pm

Transcript

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Narration: Russell Drysdale's paintings of bleak landscapes and rural struggle are icons of Australian drought.

His images from the 1940s are just as relevant these days, as much of our wheat crop shrivels to little more than hay.

Mark Horstman: What's it supposed to look like in a good year, this paddock?

Phillip Alcorn: About four-foot high and thick and full heads, full of grain and ready for harvest.

Phillip Alcorn: A good average wheat yield here would be five tonne to the hectare. This year I'll end up with point one or two of a tonne to the hectare so basically, it takes everything.

Mark Horstman: This is what much of our wheat crop looks like in drought - short, thin and barely any grain. But what if we could make wheat drought proof so it still gives good yield, even when water is very scarce.

Well, there's new hope, thanks to a chance meeting of two long-lost schoolmates.

Richard, how are you?

Graham Farquhar: I ran into Richard Richards. I'd known him from McKinnon High in Melbourne, and it turns out that we were both living in Canberra and both interested in water use efficiency

Narration: Graham Farquhar and Richard Richards discovered they were both trying to develop drought resistant plants.

Graham as a theoretical biophysicist... and Richard as a hands-on plant breeder.

Richard Richards: It's just a wonderful transfer of very clever theoretical ideas that Graham had developed into reality, and that's just fantastic

Narration: The two scientists started working together to produce a more water efficient wheat - one that would give more crop, per drop.

Graham Farquhar: He was, and is, a plant breeder and he knew that he had some wheats that differed in water use efficiency.

Narration: Water use efficiency is how much you get from the crop for the amount of water it takes to grow.

Plants transpire through small pores on their leaves called stomata. As carbon dioxide goes into the leaf, water molecules come out.

Graham Farquhar: They look like a mouth and when they are open the plant can take up more carbon dioxide but inevitably, they lose more water.

Mark Horstman: This is a wheat plant, and this is the gas exchange chamber. It's like a mini atmosphere that we can have in a lab and put a plant in.

It measures the carbon dioxide going in and the water coming out and it can tell us how much water the plant loses while it's breathing.

But not all carbon dioxide molecules are the same.

One per cent of carbon atoms are isotopes called C 13 - the rest is C 12.

Graham Farquhar: What we found to our delight was the ratio of carbon dioxide uptake to use, the water use efficiency of the leaf correlated with the composition of the carbon in the plant.

Narration: It means they can test the water-saving qualities of a plant by simply measuring C13 in the leaf.

It's all to do with photosynthesis, and the most abundant protein on Earth - called RuBisCO.

RuBisCO is the enzyme that drives photosynthesis in plants. The rate of the reaction affects which carbon isotopes are absorbed by the leaf.

The greater the proportion of C13 in the leaf, the more closed the stomata, and the less water is lost.

Their new test for carbon isotope discrimination allows them to breed wheat that grows better in drought.

This is where Richard's skills came to the fore.

Richard Richards: So this is the beginning and it's the most critical element of the whole process

Narration: And it relies on classical breeding techniques.

Richard: We have to move the pollen from each of those flowers before we cross-pollinate.

Richard: Next step is, we need to protect the wheat ear from cross pollination.

Narration: Because Richard uses different pollen from a ten-thousand-year old wheat ancestor from Persia.

The ancient plant has genes that are critical for surviving drought conditions.

Richard: You can just see some yellow anthers which contain the male parts, the pollen, and those pollen grains contain the genetic potential which has been in this plant for about ten thousand years.

Mark: And that's the raw material you can develop your new drought tolerant varieties from?

Richard: \That's right. Those genes totally recombine, they potentially can produce thousands of progeny, and every single one is different, so the secret is to have a very effective selection tool such as carbon isotope discrimination to select the very, very best.

Narration: After years of selection, they had a new wheat variety, named in honour of the artists.

Richard: It's incredible how Drysdale captured the conditions that we see now, back in 1944 as well.

Graham: What I like about her, she's stoical, but you get the impression she's not beaten by it.

Narration: Before the wheat can be released commercially, they have to test it in the paddock. And how does it go?

Richard: Wonderfully well, in fact Drysdale has been very successful in New South Wales in particular where we bred it for, and in dryer years it yields about ten per cent more than most other varieties.

Narration: With Australia's annual wheat crop worth about five billion dollars, ten percent is a potential gain of around 500 million dollars.

They're the sort of figures that wheat farmers can't ignore.

Phillip Alcorn: Certainly further west of us, farmers have been growing it and growing it very successfully. It's been a fairly large benefit to them in the dry years.

Narration: But could the wheat's performance in drought be even better if its proteins or genes are modified in the lab?

Graham Farquhar: If there was a more efficient Rubisco that for the same amount of protein was able to suck more CO2 out of the atmosphere, that would ... make a more water use efficient plant.

Narration: In the lab next door, Graham's colleague Spencer Whitney uses a biological gun to shoot DNA into a wheat leaf.

Dr Spencer Whitney: Essentially we have little DNA bullets in this little tray here, close the machine...And we put the leaf under a vacuum, and that helps the plant take up the DNA.

Mark: So you are actually going to shoot DNA into that leaf?

Spencer: That's right. Cocking the gun (boomph) the DNA has now been shot into the leaf. Direct hit!

Mark: Good shot.

Spencer: Now we can just take the plant away to actually get the plant cells which have taken up the DNA and hopefully we will get a better plant.

Spencer: If we can actually make some beneficial improvements to Rubisco in wheat, we may even be able to extend the crop regions in which we can actually grow wheat to those where water availabilities may be a little bit less.

Graham Farquhar: Yes we could use transgenic techniques to find better plants but we won't need to actually have them growing and be consumed as transgenic plants. We can achieve that same result then via the classical route once we know what we want.

Narration: And that means more varieties of drought-resistant wheat. For many farmers, it's the difference between surviving the next "Big Dry", or leaving the land.

Phillip: My hope is to be able to be here and be sustainable and be able to hand the farm on to the next generation, my sons.

If this weather pattern's going to become normal, it's going to be very, very important to our operation to find wheats that use less moisture.